TWI469382B - Structure and device of light emitting diode and method for making the same - Google Patents

Description

Light-emitting diode structure and component and manufacturing method thereof

The present invention relates to a structure, an element, and a method of fabricating the same, and more particularly to a structure, an element, and a method of fabricating the same for a light-emitting diode that is separated from a substrate by a weakened structure.

Light-emitting diodes (LEDs) have horizontal and vertical structures in their applications. Conventional horizontal LED components have current crowding in the mesa due to the arrangement of their electrodes on the same side, which leads to poor heat dissipation, which limits the amount of driving current that the LED can carry. At present, high power LEDs adopt a vertical structure.

As shown in FIG. 1A, after the LED element 102 and the mirror/adhesive layer 104 are grown by an epitaxial substrate 100, the LED element 102 is transferred to the conductive layer through the adhesive layer by wafer bonding. A carrier 108 is carried. Thereafter, as shown in FIG. 1B, the epitaxial substrate 100 is removed. Next, as shown in FIG. 1C, the metal electrode 110 is formed on the surface of the LED substrate 102 and the surface of the carrier substrate 108 on the opposite side thereof, respectively, to have a vertical structure. As shown in FIG. 1C, because of the vertical electrode configuration, the dispersion of the current I is better. Secondly, the carrier substrate 108 is generally made of a material such as tantalum, copper, aluminum, copper/tungsten, etc., which has good conductivity and good heat dissipation. Increase the operational efficiency of components.

However, the current method of separating epitaxial substrates is as in the US patent. The laser lift-off (LLO) disclosed in US 6,071,795 uses a KrF laser to irradiate the interface between the substrate and the gallium nitride layer on the epitaxial substrate side, so that the component interface absorbs sufficient energy, and The epitaxial substrate is separated. Alternatively, the epitaxial substrate may be directly polished by polishing, or the substrate may be thinned by wet etching and polishing, and then the remaining substrate may be dissolved by an etching solution. However, in the case of using the LLO method, since the control of the laser energy is not easy, it is easy to cause damage on the surface of the element. For some of the more fragile substrates such as gallium arsenide, it cannot be processed by grinding, and for some substrates such as sapphire, gallium nitride, aluminum nitride, etc., it takes a long time. Time to grind. In addition, the first method of grinding and then removing by wet etching is only applicable to a gallium arsenide or germanium substrate, but a commonly used gallium nitride, aluminum nitride or sapphire substrate has difficulty in application.

The invention provides an LED structure, an element and a manufacturing method thereof, which can separate the LED element from the epitaxial substrate.

According to an embodiment of the invention, a light emitting diode structure is provided. The light emitting diode structure includes at least a substrate, a patterned epitaxial layer and a light emitting structure. The light emitting structure is formed on the substrate through the patterned epitaxial layer, and the patterned epitaxial layer comprises a plurality of columnar structures, which can be broken during the cooling process.

Moreover, according to an embodiment of the present invention, there is provided a method of fabricating a light emitting diode element, comprising at least the following steps. First, a substrate is provided. Forming a patterned epitaxial layer on the substrate, the patterned epitaxial layer having It is made up of a specific height and consists of a number of columnar structures. In addition, a mask layer is formed on the surface of the patterned epitaxial layer such that the mask layer covers at least the sidewall of the patterned epitaxial layer. A nitride epitaxial layer is formed on the patterned epitaxial layer. A light emitting structure layer is formed on the nitride epitaxial layer to complete a first structure. Next, a conductive carrier substrate is provided and a bonding process is performed to transfer the structure to the conductive carrier substrate. Then, in the cooling process, the weakening process is performed to break the patterned epitaxial layer to form a light-emitting diode structure, including an irregular plurality of columnar structures, and the mask layer covers the surface thereof.

Embodiments of the present invention further provide a light emitting diode device including a conductive carrier substrate, a light emitting structure, a plurality of columnar structures, a dielectric layer, a first electrode, and a second electrode. The light emitting structure is located on the conductive carrier substrate. The columnar weakened structure is located on the light emitting structure. The dielectric layer covers the surface of the columnar structure. The first electrode is on the columnar structure and the second electrode is on the conductive carrier substrate.

In summary, by weakening the structure, the LED elements can be naturally separated from the epitaxial substrate due to the difference in material expansion coefficients during the process of cooling the process without using an additional process such as laser stripping. step. In addition, the LED element has an epitaxial layer of a specific thickness to allow the LED element to be naturally separated from the epitaxial substrate without rupturing the LED element.

The above and other objects, features and advantages of the present invention will become more <RTIgt;

2A to 2M are schematic views showing the manufacture of an LED element according to an embodiment of the present invention. In the figures, the layers are not drawn according to the actual scale, which only represents the relative positional relationship between the layers. In addition, the materials and the like of the layers mentioned in the embodiments are merely for convenience of understanding, and those skilled in the art can make appropriate changes or modifications.

As shown in FIG. 2A, an epitaxial layer 202, a first mask layer 204 and a second mask layer 206 are sequentially formed on a substrate 200. The epitaxial layer 202 is then used to form the weakened structure of the embodiment. . The material of the substrate 200 is, for example, single crystal sapphire, gallium nitride, germanium, tantalum carbide, gallium arsenide, gallium phosphide, zinc oxide or magnesium oxide. The sapphire substrate will be exemplified below.

In addition, in the present embodiment, the epitaxial layer 202 is made of gallium nitride. This material is for illustrative purposes only and is not intended to limit the scope of the present invention; it may be changed to be appropriate when different light emitting diode structures are used. material. For convenience, hereinafter referred to as a gallium nitride layer 202. Further, the thickness of the gallium nitride layer 202 is, for example, 0.5 to 3 nm.

Further, the first mask layer 204 is made of, for example, cerium oxide and has a thickness of, for example, 200 nm. The second mask layer 206 is made of, for example, nickel and has a thickness of about 50 to 300 nm. The first mask layer 204 and the second mask layer 206 can be used as an etching mask in subsequent processes. The materials used for the first mask layer 204 and the second mask layer 206 can be appropriately adjusted depending on the etching recipe or the like.

Next, as shown in FIG. 2B, the above components are subjected to a high temperature process. This high temperature process is, for example, a tempering process at a temperature of about 650-950 °C. By this high temperature process, the second mask layer 206 on the first mask layer 204 forms a mask ball layer 206a due to surface tension, and may include a plurality of mask balls. In the present embodiment, the mask ball layer 206a is, for example, a nickel-nano mask ball layer having a nanometer scale; each of the mask balls has a diameter of, for example, 50-350 nm, and a pitch of, for example, 100-350 nm. Each of the mask balls can be arranged in a random pattern or a regular pattern.

Next, as shown in FIGS. 2B and 2C, the first mask layer 204 and the gallium nitride layer 202 are etched by an etching method using the mask layer 206a as a mask until the underlying substrate 200 is exposed. Thereby, a patterned epitaxial layer 202a is formed. Since the mask ball layer 206a has a nanometer level, by controlling the vertical etching rate to be greater than the lateral etching rate, a nanometer-sized gallium nitride pillar layer can be formed, followed by a gallium nitride pillar layer 202a. Collected collectively. Referring to FIG. 2D, the residual mask ball 206a and the first mask layer 204a are then removed, and the removal can be performed using any type of semiconductor etching process.

The above-mentioned gallium nitride pillar layer 202a will be used as a weakened structure in the subsequent process to facilitate the subsequent weakening process; the width of each pillar is, for example, between 50 and 350 nm, and the pitch is, for example, between 100 and 350 nm, and the height is 0.5-3 μm. The arrangement may be in the form of a regular or irregular distribution, which is determined by the etched pattern of the second mask layer.

Next, as shown in FIG. 2E, on the surface of the gallium nitride pillar layer 202a, a third mask layer 210 is conformally deposited, which can be mainly used as a protective layer in a subsequent process. The material of this third mask layer 210 is, for example, cerium oxide (SiO ₂ ), and the thickness is, for example, 50 to 200 nm.

Referring to FIG. 2F, the third mask layer 210 on top of the gallium nitride pillar layer 202a is selectively etched such that the gallium nitride pillar layer 202a exposes a portion of the top surface to form a fourth mask layer 210a. The etching method can select a suitable semiconductor process such that only the third mask layer 210 near the top is removed while the etching is in progress.

Next, as shown in FIGS. 2G and 2H, a nitride epitaxial layer 212 is grown on the exposed surface of the gallium nitride pillar layer 202a by metal organic chemical vapor deposition (MOCVD) in a lateral epitaxial manner. . The nitride epitaxial layer 212 is, for example, an N-type doped gallium nitride epitaxial layer.

In addition, in order to balance the lattice mismatch, the subsequent stress factors between the LED element and the substrate, and subsequent cracking of the epitaxial element due to temperature drop, the nitride epitaxial layer 212 has a specific thickness range, for example, 0.5-3 μm. Can achieve the growth of the lattice mismatch minimized, and will not cause cracking.

Next, as shown in FIG. 2I, a semiconductor stacked layer 220 is formed on the surface of the nitride epitaxial layer 212, which is a stacked structure, for example, formed by a first doped layer, a light emitting layer and a second doped layer. . In this embodiment, the semiconductor stacked layer 220 is, for example, a P-type doped gallium nitride layer 222, a quantum well (QW) or a multiple quantum well (MQW) 224 and an N-type doped nitrogen. The gallium layer 226 is formed.

Thereafter, a conductive reflective layer 290 and a first bonding layer 230 are formed over the semiconductor stacked layer 220 to form a light emitting diode structure as shown in the left side of FIG. 2I. Referring to FIG. 2I as well, a conductive carrier substrate is additionally prepared. 250. The conductive carrier substrate 250 is made of, for example, tantalum. A second bonding layer 240 is also formed on the surface of the conductive carrier substrate 250.

Next, a wafer bonding step is performed to bond the two structures through the first bonding layer 230 and the second bonding layer 240 to each other. By this bonding step, the semiconductor stacked layer 220 and the sapphire substrate 200 are transferred onto the conductive carrier substrate 250 to form a structure A as shown in FIG. 2J, which includes the light emitting structure A1, the gallium nitride pillar layer 202a, and the substrate 200. The material of the first bonding layer 230 and the second bonding layer 240 is, for example, a tin-gold alloy (AuSn), gold, and the reflective layer and the conductive material may be selected from silver and nickel, in addition to being used for wafer bonding. Alloy materials such as platinum and aluminum. Therefore, it is not limited to a single layer material, and it is also possible to form a plurality of layers according to actual needs, which can be accomplished by those skilled in the art, and the above description is only an embodiment and is not intended to limit the present invention.

In addition, in the above manufacturing process, since the epitaxial process and the wafer bonding process for forming the semiconductor stacked layer 220 are different from each other, the first cooling process is experienced during the transfer of the machine. As described above, the thickness of the gallium nitride layer 212 can resist the difference in thermal expansion coefficient between the sapphire substrate 200 and the gallium nitride layer 212 and the semiconductor stacked layer 220, so that the temperature difference at the time of cooling can be prevented from causing uneven stress distribution. The problem of rupture caused.

Referring next to FIG. 2K, after the wafer bonding is completed, the structure A shown in FIG. 2J is subjected to a second cooling process, that is, the weakening process of the present invention. This cooling process is, for example, gradually lowering the bonded structure A to ambient temperature, that is, about room temperature. Similarly, the substrate 200 and the carrier substrate 250 The coefficient of thermal expansion is different, so when the environment is changed from the temperature at which the wafer is bonded (the junction is gold/tin, the temperature is about 350-450 ° C) to 28 ° C within 60 minutes, the stress between the materials The light-emitting structure A1 is caused to be between the weakest interfaces in the structure A; that is, the portion 260 between the gallium nitride pillar layers 202a is naturally broken to form an irregular plurality of columnar structures, and the sidewall has a fourth mask. Coverage of layer 210a.

In addition, the fracture surface of the interface 260 does not necessarily have to be fractured in a homogeneous manner. The fracture interface surface 265 of FIG. 2L is only a fracture interface, and is not intended to limit the present invention. Further, the fracture interface surface 265 is formed on the surface of the light-emitting structure A1, so that the light extraction efficiency can be improved by destroying the total reflection angle at the time of light emission. Therefore, the present invention can achieve the effect of separating the light emitting diode from the substrate 200 and achieving an increase in luminous efficiency without requiring an additional process.

Finally, an N-type electrode 280 is formed at an appropriate position on the surface of the element, and a P-type electrode 270 is formed on the surface of the ruthenium substrate 250, as shown in FIG. 2M, to form a light-emitting diode element B. For example, the electrodes may be disposed at appropriate locations on the fracture surface of the conductive carrier substrate 250 and the gallium nitride pillar layer 202a.

The light-emitting diode element of the present embodiment is exemplified by a gallium nitride material, but may be replaced with other suitable light-emitting materials and an epitaxial substrate. For example, a gallium arsenide substrate can be used to grow aluminum gallium indium phosphide (AlGaInP), or a germanium substrate can be used to grow gallium nitride. Therefore, the application is not limited to gallium nitride or sapphire substrates.

In summary, by weakening the structure, the light-emitting structure can naturally be removed from the epitaxial substrate due to the difference in material expansion coefficient during the process of cooling. Separate without having to take advantage of additional process steps such as laser stripping. In addition, the light-emitting structure has an epitaxial layer of a specific thickness, and thus can withstand cracking problems caused by uneven stress distribution when the temperature is lowered due to a difference in thermal expansion coefficient between the substrate and the semiconductor stacked layer.

Although the present invention has been disclosed in the above preferred embodiments, it is not intended to limit the invention, and any one of ordinary skill in the art can make some modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of the invention is defined by the scope of the appended claims.

100‧‧‧ epitaxial substrate

102‧‧‧LED components

104‧‧‧Mirror/adhesive layer

108‧‧‧ Carrier substrate

110‧‧‧Metal electrodes

200‧‧‧Substrate

202‧‧‧ epitaxial layer

202a‧‧‧ patterned epitaxial layer

204‧‧‧First mask layer

204a‧‧‧Residual first mask layer

206‧‧‧Second cover layer

206a‧‧‧mask ball layer

210‧‧‧ Third mask layer

210a‧‧‧4th curtain layer

212‧‧‧ nitride epitaxial layer

220‧‧‧Semiconductor stack

222‧‧‧P-type doped GaN layer

224‧‧‧Quantum Well/Multiple Quantum Wells

226‧‧‧N-doped GaN layer

230, 240‧‧‧ first and second bonding layers

250‧‧‧ Conductive carrier substrate

260‧‧‧ fracture interface

265‧‧‧ fracture interface surface

270‧‧‧P type electrode

280‧‧‧N type electrode

290‧‧‧ Conductive reflective layer

1A to 1C are conventional light emitting diode structures and their fabrication drawings.

2A to 2M are schematic views showing the manufacture of an LED element according to an embodiment of the present invention.

202a‧‧‧ patterned nitride epitaxial layer

212‧‧‧ nitride epitaxial layer

222‧‧‧P-type doped GaN layer

224‧‧‧Quantum Well/Multiple Quantum Wells

226‧‧‧N-doped GaN layer

230/240‧‧‧bonding layer

250‧‧‧ Conductive carrier substrate

Claims (9)

A method for fabricating a light emitting diode device, comprising: providing a substrate; forming a patterned epitaxial layer on the substrate; and the patterned epitaxial layer is formed by a plurality of columnar structures; forming a mask layer on The surface of the patterned epitaxial layer, wherein the mask layer covers at least a sidewall of the patterned epitaxial layer; a nitride epitaxial layer is formed on the patterned epitaxial layer; and a light emitting structure layer is formed on the nitride Forming a first structure on the epitaxial layer; providing a conductive carrier substrate, and performing a bonding process to transfer the first structure to the conductive carrier substrate; and performing a weakening process by a cooling process Destructing the patterned epitaxial layer, wherein forming the patterned epitaxial layer further comprises: forming an epitaxial layer on the substrate; forming a first mask layer on the epitaxial layer; forming a second mask a curtain layer on the first mask layer; performing a high temperature process to form the second mask layer to form a mask ball layer, wherein the mask ball layer comprises a plurality of mask balls; and the mask layer For the mask, remove part of the first mask and the Lei Layer is patterned to form the epitaxial layer. The system for producing a light-emitting diode element as described in claim 1 The method comprises a method in which each of the mask balls in the mask ball layer has a diameter of 50-350 nm and a pitch of 100-350 nm, and each mask ball has a diameter of 50-350 nm and a pitch of 100-350 nm. The method for manufacturing a light-emitting diode element according to claim 1, wherein each of the columnar structures has a specific height, wherein the specific height is 0.5 to 3 μm, the width is 50-350 nm, and each of the plurality The columnar structures have a pitch of 100-350 nm. The method of manufacturing the light emitting diode device of claim 1, wherein the forming the mask layer further comprises: conformally forming a third mask layer on the patterned epitaxial layer; and removing the A portion of the third mask layer is patterned on top of the epitaxial layer. The method for producing a light-emitting diode element according to claim 1, wherein the nitride epitaxial layer has a thickness of 0.5 to 3 μm. The method for fabricating a light-emitting diode device according to claim 1, wherein the forming the light-emitting structure further comprises sequentially forming a first doped layer, a light-emitting layer and a second doped layer, wherein the first doped layer The conductivity of the second doped layer is different, wherein the luminescent layer is a quantum well layer or a multiple quantum well layer. The method for manufacturing a light-emitting diode element according to claim 1, further comprising: forming a first bonding layer on the light-emitting structure layer; forming a second bonding layer on the conductive carrier substrate; And completing the bonding process by the first and the second bonding layer. The system for producing a light-emitting diode element as described in claim 1 The method further includes forming a first electrode and a second electrode respectively on the surface of the conductive carrier substrate and the weakened structure, wherein the first electrode and the second electrode have different conductivity types. The method for fabricating a light-emitting diode element according to claim 1, wherein the conductive carrier substrate has a different thermal expansion coefficient from the patterned epitaxial layer or the light-emitting structure.